1. Field of the Invention
The present invention relates to a vacuum pump driven by a motor. More particularly, it relates to an improvement in a vacuum pump of a type in which a slide shaft provided with a diaphragm is reciprocated at a predetermined stroke by means of a cam plate rotated by a motor.
2. Description of Prior Art
FIG. 1 shows a conventional vacuum pump. The conventional vacuum pump has a bearing casing 12 holding a bearing 1A which supports a motor shaft 2 in a freely rotatable manner and a slide shaft 6 provided at its one end with discharge valves 17 and a diaphragm 7 which are essential parts of the vacuum pump. A cam plate 3 connected to the motor shaft 2 is positioned between the bearing 1A and the other end of the slide shaft 6 to cause reciprocating movement of the slide shaft 6 at a predetermined stroke. In the conventional vacuum pump, use of a relatively thick cam plate rendered the length of the vacuum pump in the axial direction to be large and the demand for forming the vacuum pump into a compact form has been restricted.